19,514 research outputs found
One-loop Neutron Electric Dipole Moment from Supersymmetry without R-parity
We present a detailed analysis together with exact numerical calculations on
one-loop contributions to neutron electric dipole moment from supersymmetry
without R-parity, focusing on the gluino, chargino, and neutralino
contributions. Apart from the neglected family mixing among quarks, complete
formulae are given for the various contributions, through the quark dipole
operators, to which the present study is restricted. We discuss the structure
and main features of the R-parity violating contributions and the interplay
between the R-parity conserving and violating parameters. In particular, the
parameter combination , under the optimal
parametrization adopted, is shown to be solely responsible for the R-parity
violating contributions in the supersymmetric loop diagrams. While
could bear a complex phase, the latter is not
necessary to have a R-parity violating contribution.Comment: 43 pages Revtex with 15 eps- and 4 ps- figure files incoporated;
proofread version to be published in Phys. Rev.
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Research on VCSEL interference analysis and elimination method
Laser methane gas sensors have been increasingly accepted in coal mine safety monitoring. Most laser spectroscopic methane gas sensors are based in BFB lasers at around 1650nm. However, they suffer from high power consumption and high cost due to temperature control is required for laser diode operation at constant temperature. VCSEL lasers have offered low operation current and low power consumption when operating at non-TEC mode. However, it is found that the interference noise is critical for laser methane detection. This paper report typical results of the laser diode ripple characterization method and methods of noise reduction methods are discussed
Ultrafast optical control of magnetization in EuO thin films
All-optical pump-probe detection of magnetization precession has been
performed for ferromagnetic EuO thin films at 10 K. We demonstrate that the
circularly-polarized light can be used to control the magnetization precession
on an ultrafast time scale. This takes place within the 100 fs duration of a
single laser pulse, through combined contribution from two nonthermal
photomagnetic effects, i.e., enhancement of the magnetization and an inverse
Faraday effect. From the magnetic field dependences of the frequency and the
Gilbert damping parameter, the intrinsic Gilbert damping coefficient is
evaluated to be {\alpha} \approx 3\times10^-3.Comment: 5 pages, 3 figures, accepted for publication in Phys. Rev.
Gamma-ray emission from the globular clusters Liller 1, M80, NGC 6139, NGC 6541, NGC 6624, and NGC 6752
Globular clusters (GCs) are emerging as a new class of gamma-ray emitters,
thanks to the data obtained from the Fermi Gamma-ray Space Telescope. By now,
eight GCs are known to emit gamma-rays at energies >100~MeV. Based on the
stellar encounter rate of the GCs, we identify potential gamma-ray emitting GCs
out of all known GCs that have not been studied in details before. In this
paper, we report the discovery of a number of new gamma-ray GCs: Liller 1, NGC
6624, and NGC 6752, and evidence for gamma-ray emission from M80, NGC 6139, and
NGC 6541, in which gamma-rays were found within the GC tidal radius. With one
of the highest metallicity among all GCs in the Milky Way, the gamma-ray
luminosity of Liller 1 is found to be the highest of all known gamma-ray GCs.
In addition, we confirm a previous report of significant gamma-ray emitting
region next to NGC 6441. We briefly discuss the observed offset of gamma-rays
from some GC cores. The increasing number of known gamma-ray GCs at distances
out to ~10 kpc is important for us to understand the gamma-ray emitting
mechanism and provides an alternative probe to the underlying millisecond
pulsar populations of the GCs.Comment: 22 pages, 7 figures, 2 tables; ApJ, in pres
Continuous volumetric imaging via an optical phase-locked ultrasound lens
In vivo imaging at high spatiotemporal resolution is key to the understanding of complex biological systems. We integrated an optical phase-locked ultrasound lens into a two-photon fluorescence microscope and achieved microsecond-scale axial scanning, thus enabling volumetric imaging at tens of hertz. We applied this system to multicolor volumetric imaging of processes sensitive to motion artifacts, including calcium dynamics in behaving mouse brain and transient morphology changes and trafficking of immune cells
A NuSTAR Observation of the Gamma-ray Emitting Millisecond Pulsar PSR J1723-2837
We report on the first NuSTAR observation of the gamma-ray emitting
millisecond pulsar binary PSR J1723-2837. X-ray radiation up to 79 keV is
clearly detected and the simultaneous NuSTAR and Swift spectrum is well
described by an absorbed power-law with a photon index of ~1.3. We also find
X-ray modulations in the 3-10 keV, 10-20 keV, 20-79 keV, and 3-79 keV bands at
the 14.8-hr binary orbital period. All these are entirely consistent with
previous X-ray observations below 10 keV. This new hard X-ray observation of
PSR J1723-2837 provides strong evidence that the X-rays are from the
intrabinary shock via an interaction between the pulsar wind and the outflow
from the companion star. We discuss how the NuSTAR observation constrains the
physical parameters of the intrabinary shock model.Comment: Accepted for publication in ApJ. 5 pages, 3 figure
The Ultraluminous X-ray Sources near the Center of M82
We report the identification of a recurrent ultraluminous X-ray source (ULX),
a highly absorbed X-ray source (possibly a background AGN), and a young
supernova remnant near the center of the starburst galaxy M82. From a series of
Chandra observations taken from 1999 to 2005, we found that the transient ULX
first appeared in 1999 October. The source turned off in 2000 January, but
later reappeared and has been active since then. The X-ray luminosity of this
source varies from below the detection level (~2.5e38 erg/s) to its active
state in between ~7e39 erg/s and 1.3e40 erg/s (in the 0.5-10 keV energy band)
and shows unusual spectral changes. The X-ray spectra of some Chandra
observations are best fitted with an absorbed power-law model with photon index
ranging from 1.3 to 1.7. These spectra are similar to those of Galactic black
hole binary candidates seen in the low/hard state except that a very hard
spectrum was seen in one of the observations. By comparing with near infrared
images taken with the Hubble Space Telescope, the ULX is found to be located
within a young star cluster. Radio imaging indicates that it is associated with
a H II region. We suggest that the ULX is likely to be a > 100 solar mass
intermediate-mass black hole in the low/hard state. In addition to the
transient ULX, we also found a highly absorbed hard X-ray source which is
likely to be an AGN and an ultraluminous X-ray emitting young supernova remnant
which may be related to a 100-year old gamma-ray burst event, within 2 arcsec
of the transient ULX.Comment: 9 pages, 8 figures. Accepted for publication in Ap
Analysis of Microstrip Lines with Alternative Implementation of Conductors and Superconductors
An analysis of microstrip line structures in which either the strip or the ground plane or both are made of a high Tc superconductor is presented. The effect of implementation of a superconductor to the strip and the ground plane is explained with the calculation of a conductor loss of the structure by the Phenomenological Loss Equivalence Method (PEM). The theoretical values are compared with the experimental results from a ring resonator which is made of a gold ground plane and a high Tc superconductor, YBa2Cu3O(7-x), strip
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